<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
     #lamp {
            height: 140px;
            width: 530px;
            border: 1px solid #369;
        }
        #red,
        #green,
        #yellow {
            width: 120px;
            height: 120px;
            border-radius: 50%;
            background-color: gray;
            float: left;
            margin-left: 10px;
            margin-top: 10px;
        }
        #count {
            width: 120px;
            float: left;
            height: 120px;
            margin-left: 10px;
            margin-top: 10px;
            text-align: center;
            line-height: 120px;
           font-size: 60px;
        }
    </style>
</head>
<body>
    <div id="lamp">
        <div id="red"></div>
        <div id="yellow"></div>
        <div id="green"></div>
        <div id="count"></div>
    </div>
</body>
</html>
<script>
    var lamp = {
        red: {
            obj: document.getElementById('red'),
            timeout: 30,
            style: ['red', 'gray', 'gray'],
            next: 'green'
        },
        yellow: {
            obj: document.getElementById('yellow'),
            timeout: 5,
            style: ['gray', 'yellow', 'gray'],
            next: 'red'
        },
      green: {
           obj: document.getElementById('green'),
            timeout: 10,
            style: ['gray', 'gray', 'green'],
            next: 'yellow'
        },
        changeStyle(style) {
            this.red.obj.style.backgroundColor = style[0]
            this.yellow.obj.style.backgroundColor = style[1];
            this.green.obj.style.backgroundColor = style[2]
        }
    }
    var count = {
        obj: document.getElementById('count'),
        change: function (num) {
            this.obj.innerHTML = (num < 10) ? ('0' + num) : num;
        }
    }
    var now = lamp.green;
    var timeout = now.timeout;
    lamp.changeStyle(now.style);
    count.change(timeout);
    function me(){
        if (--timeout <= 0) {
                now = lamp[now.next];
                timeout = now.timeout;
                lamp.changeStyle(now.style);
            }
        count.change(timeout)
        setTimeout('me()', 1000);
    }
    me();
</script>
